Electric discharge device construction



June 20, 1950 LEMMERS 2,512,280

ELECTRIC DISCHARGE DEVICE CONSTRUCTION Filed March 10, 1947 lnvemTor-z Eugene Lemmers,

b UM 0 JW His ATTorn e3.

Patented June 2Q, 1950 ELECTRIC DISCHARGE DEVICE CONSTRUCTION Eugene Lemmers, Cleveland Heights, Ohio, as- .signor to General Electric Company, a corporation of New York Application March 10, 1947, Serial No. 733,595

v This invention relates to electric discharge devices of the type employing ionizable mediums such as gases or vapors, and more particularly to base and starting strip constructions for such devices.

The present application is a continuation in part of my copending application Serial No. 671,189, filed May 21, 1946, now abandoned, and which is assigned to the assignee of this application.

One object of my invention relates to a unitary base and circuit controlling element for anelec- 'tric device and which comprises at least one terminal for connection to a source of power and in which an integrally formed portion in electrical contact with the terminal affords a predetermined electrical resistance.

Another object of my invention is to provide a new and improved base construction for electric discharge lamps and similar devices wherein the base, consisting of a composite substance of a predetermined resistance value, serves as a current limiting device or as a constitutent part of the electrical circuit of the electric discharge lamp or part of an associated circuit.

Another object of my invention is to provide a new and improved starting arrangement for electric discharge lamps and similar devices wherein a starting strip is utilized to facilitate starting.

A further object of my invention is to provide a starting arrangement for electric discharge lamps and similar devices of the type employing an external starting. strip or stripe to facilitate starting, and means for minimizing shock hazards attending operation of the device.

A still further object of my invention is to provide a starting arrangement for electric discharge lamps and similar devices wherein a starting strip is utilized to facilitate starting, and wherein at least one of the bases of said device functions as a current limiting means for the starting strip.

Another still further object of my invention is to provide a starting arrangement for electric discharge lamps and similar devices wherein a starting strip is utilized to facilitate starting, and wherein at least one of the bases serving as a current limiting element consists of a composite substance of a predetermined resistance value.

Further features and advantages of my invention will appear from the following detailed description of species thereof. For a better understanding of my inventionvreference may be had to tlie following description taken in connection 4 Claims. (Cl. 315-60) with the accompanying drawings and its scope will be pointed out in the appending claims.

Fig. 1 is a side elevation of a glow discharge device incorporating my invention. Fig. 2 is a perspective view of the bottom of the base of the glow discharge devices shown in Fig. 1 and shows more clearly the construction features of the base incorporating my invention. Fig. 3'is a diagrammatic view of an electric discharge device and means to facilitate starting thereof incorporating my invention. Fig. 4 is a similar diagrammatic view illustrating a modification of my invention. Figs. 5 and 6 show a partially sectionalized electric discharge device and means to' facilitate starting thereof incorporating arrangements of Figs. 3 and 4, respectively. Fig. '3' is a perspective view of a base for an electric discharge device illustrating a modification of my invention.

Referring to Fig. 1, I have there illustrated one embodiment of my invention as applied to an electric discharge device or glow lamp I. The :lamp I comprises a vitreous envelope 2 having sealed into the end thereof a stem 3, which may comprise a stem press or squeeze 4 employed to furnish a mechanical support for lead-in wires 5 and 6 and to fuse and secure these wires through 'stem 3.' Lead-in wires 5 and 6, serve as supports for electrode structure including a pair of spaced electrodes 1 and 8, defining therebetween a gap 9. Electrodes I and 8 may be constructed of preformed sheet material such as nickel, having a substantial concavity into which the upper part of the stem assembly, or particularly the stem squeeze extends, thereby reducing the axial length of the electrode structure and providing mechanical features adaptable for supporting the electrodes. A unitary base structure is provided comprising a non-conductive composition including a resistance element integral therewith of predetermined value, or apredetermined conductive composition or material of a relatively high specific resistivity. 'In Figs. 1 and 2, a base I0 may embody aresistor II therein of a relatively low specific resistivity, for example 3500 ohms, which is electrically connected to one end of lead-in wire 5 and forms with lead-in wire 5 a conductive member of predetermined resistance for connection to an external source, and serves as a ballast for limiting the arc discharge current of glow lamp I. Base I0 serves conjointly as an insulator for contact terminals or pins I2 and I3 and as a conductive path by virtue of resistor I I of predetermined resistive value for ballasting glow lamp I.

An exhaust tube [4 as shown in Fig. 1 is provided for exhaustion and sealing of envelope 2. A suitable atmosphere, such as a gas or a vapor is provided within the sealed envelope 2. This atmosphere, for example, may consist of argon containing 5 to 20 per cent of nitrogen at a pressure of 6 to 20 millimeters of mercury. A preferable mixture giving exceptionally good results has been found to be neon containing about 0.8

of a per cent of argon at a pressure of 35 millie.

meters of mercury.

Fig. 2 is a perspective view of the bottom of the base it of the glow discharge device shown in Fig. 1, and shows more clearly the construction features of the base incorporating my inven tion. As one example with respect to the construction of base shown in Fig. 2 my inven-.- tion may be carried out by using any suitable plastic moulding compound to which may be added an ingredient such as a powdered electrioollr ooe luot vo i red ent to fior o tho roin orm oos a prede e m ned r ist ncelylore specifically by the addition of a suitable conductive ingredient the resulting composition bcdy portion is given a predetermined specific oloo ioal res y. nd th exa t a u of h resistance afiorded by base construction is determined by the base configuration, thickness, len h of pat o o Th ran e os s an es which may be used for ballasting a glow lamp in th s manner and which may be obtained by practioinz my invention range from about 1000 ohms to 1 meg'ohm. These values of resistance vary the characteristics of the lamp, the type of plastic used and the amount of conductive. ingredient used therein.

In making a base having a predetermined resistance, I may employ plastic moulding com,- pounds such as those comprising phenol-furiural resins or phenolic resins. Furthermore, I may employ a plastic moulding compound comprising a phenol-.furfural and formaldehyde to which'may be added a plasticizer such as dibutyl phthalate, a lubricant such as hexamoth: y ons "tot am e. an a ce ra o suc s onzov peroxide, and a fillersuch as wood flour. r In order to modify the characteristics of the moulding compound'employed in producing the base for glow lamp l and to produce therein a ath forming a resistor having a predetere mined electrical'conductivity commensurate with the above described requirements, I provide a conductive ingredient in the moulding. compound to produce the desired resistive characteristics thereof. For example, this conductive ingredient may be a powdered conductive material such as carbon or powdered metals. The percentage by weight of the powdered ingredient employed'in mculding compounds is determined by the degree of electrical conductivity desired. In forming the base, conductive moulding compound of a rela iv ly high snoo o. re t it he inserted into the mould and an added conductive moulding compound of a relatively low specific resistivity embodying resistive material such as powdered conductive material as mentioned herein above, may be added to form the conduct ive path ll serving as the ballast or resistor II or s w amp In Fig. 3, the discharge device i therein com,- prises an elongated tubular or cylindrical envelope 16 having sealed into the ends thereof the thermi i e c rodes I1 and I8 w ioh may be o he fil m nta y n osoh heroi lu t a ed as comprising a coil, preferably in the term or. a

coiled coil of tungsten wire activated with the usual mixture of barium and strontium oxides. Sealed into the ends of device l5, lead-in wires i9, 29 and 2!, 22 electrically connect thermionic electrodes 57 and i8, respectively. Suitable provision may be made, not shown, for connecting these lead-in wires to a source or" electrical supply for heating the electrodes wherebythey are brought to a glowing and emitting temperature and for starting and maintaining the gaseous discharge between the two electrodes. The envelope it contains an ionizable medium. This ionizable medium may comprise a rare gas like krypton, neon, argon or mixtures thereof at a pressure of a few millimeters and a small quantity of mercury which, during operation of the lamp, has a low pressure of the order of ten microns. The device I5 may be a low pressure positive column lamp of the fluorescent type with a suitable phosphor or fluorescent coating. This flnoroso n coatin u on e tatio by th aoiati n o o oosrl y an elect io discharge beeen th loo r ol tra form the h r erwave ra iat o due to the d s harge into longer- Wave radiation such as radiation within the visible range. For ease or" starting, a strip or stripe 23 or ho oti ma er a s ap li d to t sor iace of device IS.

in some of the prior art arrangements it has been the practice to allow the starting strip to fl at. at is the startin strip is. Pr jected along the. len th or h d sohoree d ices and. in c os p ox m y o the. cools ho e Resu ting l i o br a d w oltage w re arou d the. va ue o 20 ol s for a s wa t fluoresc nt amp o bo h/ s, hoste the mionio lec r des By con.- n ctin one end of e. start n strip diro lyto one oat dh rm on o e ec od o he dis har e devi a reakdown vo tage. aroun th a e o 16 v s is obtained- Bed ion in. b eak own v e ar also obtain d w th am of ary ng sizes by a similar connection. This added ad.- an a o w ot practical howeve d to tho sh ok hazard pr e u n lam o rat on- In a no w th. o as ect f in ention, I provi e m ns o oonnectine the starti g st ip t n o I nore o t e e e trodes n rder to reduce h startin vol a e, req iired to in tiate are oisoharg i be e n the e ectrodes. In additicn Iprovide arrangements and connections by v u of. wh ch the. above es ibed, low-s ar n voltage .is tain d a d. wh ch als af ords a hi hly de irable feature of reducing o som p to v e m natin p rson el. hook hazard. in

cident to the p es t he s arti str p 23 on the terio urfa e of the en elop Genera l sp aking, I effect h desir d. co ec on. between t e s arting r p 23 n one o the elec odes by he s of moans. ioroine a Pr deter noo esi tan e o elati ly high value. For exampl in aocordeno wi h one aspect of my invention I may employ separate or indi.- vi u l in po an omoans. 2 4. such a resistanc s. n uc o s. or o o oitan os hav ng relat ely lar e pr t rmined va ues, f the. order or moso s- I ha ound. tha or p l a on to the so watt siz fluores nt amps r s stive alues. in om one. to o mogo ms. and p efer b y f m 2 o 8 moe hms. r s t fa tory tor the a ed ur ses or reduc s arti vol an at he same time se ving as, cu rent im n ean o reduc pers nnel. shook hszarcl- It possib e ha tho hosting, of one. of the electrodes may be dispensed with. In that event, it is feasible to dispense with the supplying of heating current to electrode ll, 1. e., the electrode connected through impedance 24, to the starting strip 23.

Fig. 4 incorporates the same above-described corresponding parts of Fig. 3 with the addition of an impedance 25, which, as in Fig. 3, may be a resistance, inductance, or capacitance having a relatively large predetermined ohmic value of the order of megohms, and connected to the starting strip 23 in such a manner as to form a series connection between thermionic electrode [8 and the starting strip 23. Thus, a voltage divider is provided across the thermionic electrodes I1 and i8 and includes the starting strip 23 as one element thereof. By utilizing two resistors 24 and 25, it is possible by selecting the proper resistance ratio between the two resistors, to vary the breakdown voltage between given limits. This reduction in breakdown or starting voltage is particularly evident where this arrangement is used with lamps employing cathode heating or cathode pre-heating by means of separate cathode heating circuits or auxiliary means. For example, a 40 watt fluorescent lamp with the resistors 24 and 25 both megohms in value the breakdown voltage of the ionizable medium would be 240 volts; if the megohm resistance ratio was 5 to 2 the breakdown voltage would be 170 volts; and if the megohm ratio was 5 to 1 the breakdown voltage would be 150 volts. Thus, a means is available to either aid or resist the breakdown of the discharge device.

Fig. 5 incorporates the same above-described corresponding parts of Fig. 3 except the resistor 24 is replaced by a base 25 which functions as the current limiting or impedance means and a base 21 of the type commonly used in the lamp discharge industry. Contact terminals or pins 28, 29 and 30, 31 are connected to the associated lead-in wires. the plastic type presently used in the lamp discharge industry with an associated high resistance conductive path in the form of a layer 32 of conductive material applied to the irmer side of the base and forming an electrical connection between the starting strip 23 and the associated electrode l1. Aquadag, India ink, or some similar conductive material may be painted or sprayed on the entire inner surface of the plastic base to form the conductive path of a predetermined resistive value. Thus by extending the starting strip 23 to the base line of the discharge device, on that end of the envelope It to which the resistive coated base is to be applied, electrical contact may be made between the resistive coated base and the starting strip 23. To prevent any possibility of a basing cement 33 breaking this electrical connection it becomes practical to substitute a given per cent of carbon for the usual filler in the basing cement formula. One example of a, conductive basing cement incorporating these characteristics is a mixture containing 15 to 17 per cent of a resin consisting of one part of a commercial plastic moulding compound, 4 parts rosin, and 6 parts shellac, and 83 to 85 per cent marble flour filler of which 8 to 20 per cent of the filler would be graphite flakes. The layer 32 of conductive material applied to the inner side of the base may be in the form of a thin, narrow conductive path sprayed or painted on the base to Base 26 may be one of- 6 form a conductor integral therewith of given dimensions and predetermined resistivity.

Fig. 6 incorporates the above-described corresponding parts of Fig. 4 except resistors 24 and 25 are replaced by bases 34 and 35 which function as the current limiting or impedance means and also comprise elements of a voltage divider. Bases 34 and 35 are formed with a pair of contact terminals or pins 36, 31 and 38, 39 respectively, to which the lead-in wires I9, 20 and 2!, 22 are respectively connected. The base structure consists of a composition metallic or otherwise having a relatively high specific resistivity, thus provided a high resistance conductive path between the starting strip 23 and the associated electrode I! or I8. In this manner the bases serve conjointly as an insulator for the contact terminals or pins and as conductive paths of predetermined resistive value for connection to the starting strip 23.

As one example, with respect to the construction of bases 34 and 35, my invention may be carried out, as hereinbefore mentioned by using any suitable plastic moulding compound to which may be added an ingredient such as a powdered electrically conductive ingredient to aiford to the resulting or formed bases a predetermined resistance. More specifically, by the addition of a suitable conductive ingredient the resulting composition is given a predetermined specific electrical resistivity. This conductive ingredient may be a powdered conductive material such as carbon, or powdered metals. The percentage by weight of the powdered ingredient employed in molding compound is determined by the degree of electrical conductivity desired. I have found that in order to obtain the above described ohmic values for the conductive path that from 1 to 10 per cent by weight of carbon may be used to produce electrical resistivities of the proper magnitudes.

Fig. 7 is a perspective view of a base 40 for an electric discharge device illustrating a modification of my invention. I have there shown a unitary base having a shape of the type commonly used in the fluorescent lamp industry except the base comprises a metallic shell M embodying a fiat plastic body portion or disc 42 of a predetermined electrical resistance moulded or formed integral therewith. Disc 42 supports a pair of contact pins or terminals 43 and serves conjointly as an insulator therefore and as a conductive path of predetermined resistive value for connection through shell M to a starting strip or stripe on a fluorescent lamp such as that shown in Figs. 5 and 6. Shell 4| for example may be an aluminum alloy or brass coated steel.

The structures particularly shown and described in connection with Figs. 1, 2, 5, 6 and 7 are claimed separately in my divisional application Serial No. 34,067 filed June 19, 1948.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In combination, an electric discharge device employing an ionizable medium and comprising an envelope and a plurality of electrodes at least one of which is of the thermionic type, a starting strip on the surface of said envelope, and means for establishing said strip at a potential optimum for starting an arc discharge between said electrodes upon energization thereof comprisinga voltage divider connected across said electrodes and including said strip as one element thereof and also including an impedance means of high ohmic 2&123

and. terminating within the vicinities thereof,v

and means for connecting said strip to said electrode comprising a pair of impedance means of difierent ohmic values each connected between said strip and a difierent one of said electrodes.

3. In combination, an electric discharge device employing an ionizable medium and comprising an envelope and a pair of thermionic pre-heated electrodes, a starting strip on the surface of said envelope, and means for establishing said strip at a potential optimum for starting an arch discharge between said electrodes upon, impressing a voltage thereacross comprising a voltage divider connected to both of said electrodes and including said strip as an element thereof and also including an impedance means of high ohmic value between each end of the said strip and a different one of said electrodes.

I 4. An electric. discharge device comprising an elongated envelope containing an ionizable medium and widely spaced electrodes at least one of which is of the thermionic type, means for facilitating the establishment of an arc discharge between s-aid electrodes comprising a starting strip extending along said envelope between said electrodes and terminating within the vlicinities thereof, and means connecting said strip to said electrodes comprising a pair of impedance means each connected between said strip and a difierent one of said electrodes, said impedance means having values of resistance in the order of megohms and differing in a ratio of at least about 5 to 2.

EUGENE LEMMERs.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,984,428 Pirani Dec. 18, 1934 2,010,879 Mutsaers Aug. 13, 1935 2,146,579 Inman Feb. 7, 1939 2,432,219 Vang Dec. 9, 1947 

